The conventional frame member of the above type is formed from iron or stainless steel. The frame member is formed by bending a steel plate of a suitable thickness and proper length by a press or bender to make a simple long structure, and connecting a plurality of such structures to each other, for example.
The conventional frame member is also formed by an extrusion molding from aluminum. The frame member of this type is advantageous in that it can easily be formed to have any complicated shape as desired.
The traveling rail laid under a conveyor chain is formed by working or extrusion molding, for example. For installing the traveling rail to the frame member, the traveling rail is put on the frame member, and fixed to the latter with a plurality of screws at longitudinal predetermined intervals. Alternatively, as shown in FIG. 16, a traveling rail 50 formed by extrusion molding is fitted onto the flat end of a frame member 51, the traveling rail 50 is caused by its own elastic force to catch the end of the frame member 51, and then the end of the traveling rail 50 is fixed to the frame member 51 with screws.
However, the conventional frame member formed from iron or stainless steel is not advantageous in that it can only have a relatively simple structure. To meet the requirements for an appropriate precision of working and rigidity, the frame member has to be formed from a relatively thick plate material. In this case, however, it is difficult to reduce the weight of the frame member and the manufacturing cost. If the frame member required to have a predetermined precision of working and rigidity has no sufficient precision and rigidity to meet the requirements, a step will possibly take place at the connection between the frame members, with the result that articles being conveyed will cause a noise each time they are moved on the rail, they cannot be conveyed at any constant speed and it will be overturned in some cases.
Further, since the conventional frame member incurs a sharp edge in the process of cutting as the case may be, the workers should always be careful when handling such frame members during work at a site of installation. In the worst case, the workers may possibly be bodily injured seriously by such sharp edges.
Also, when assembling such frame members, bolts and nuts at the guide bracket and connections, protruding from the lateral sides of the frame members not in the worker's field of view as the case may be, will possibly hurt the workers unexpectedly. More particularly, since the guide bracket has to be installed where fixing holes are performed, it is necessary to re-form new fixing holes for alignment with holes in the guide bracket if the performed fixing holes are not correctly aligned with the holes in the guide bracket, which will lead to more time of installation and thus larger costs than estimated.
Furthermore, the frame formed from aluminum by extrusion molding is likely to react with moisture or water in an environment where the conveyor system is in operation to produce aluminum oxide compound, has a structure from which water cannot be drained. So, the remaining water in the conveyor system will decay and be unsanitary. Particularly, the aluminum oxide compound produced in the environment where the conveyor system is in operation is very harmful. In industries of food processing and any other fields of industry, it is not desirable from the sanitary point of view to work in any environment where such harmful substance will possibly take place.
Additionally, when the traveling rail is increasingly abraded, its fasteners such as screws are partially (at the head thereof, for example) exposed to be in contact with the sliding surface of the conveyor chain, which will possibly cause the conveyor chains to abnormally be abraded, conveying speed to be irregular or abnormal sound to take place. Also, in case the frame member is caught by the traveling rail under the own elastic force of the latter, the traveling frame will be dislocated laterally in relation to the frame member in some cases if the elastic force of the traveling rail is not sufficiently large. On the contrary, if the elastic force of the traveling rail is too large, the traveling rail cannot be fitted onto the frame member easily or to a predetermined position as the case may be. In such a case, the convey chains cannot move smoothly, causing heat generation, abnormal abrasion, vibration, noise, etc.